Why your hands swell while hiking: the real reason

The myths of why hands swell while hiking

You’re five miles into a hike with a group of friends. You’ve never been hiking before and it sounded adventurous and fun and a great way to to get out and have fun with friends, enjoy being outside, and relax for a bit. And you’re having a great time with the exception of a weird feeling in your hands. Your wedding ring and watch are getting tight and your skin feels taut. Your arms feel bloated and you look down and sure enough you’ve got big old sausage fingers. Are you dying? Do you need to turn around and race to the hospital? Maybe you have cell service and after you post a quick pic to insta you do a quick WebMD search. It says you have heart failure or this weird thing called thrombosis. Now you’re worried and want to go back so you can do more internet searching before you head to the ER. When you get home you dig deeper in your internet searching and get more specific. Instead of just searching hand swelling, you search had hands swell while hiking and find an Outside Magazine article, where you may learn that you’re suffering from hyponatremia. You find a facebook thread of loads of confident expert internet commenters recommending the cure-all tip of hydration or electrolytes.

But nearly all this information you’ll find is absolutely, jarringly, painfully wrong, so I hope this article becomes the one to top out on the google searches so maybe some people will learn the real answer, and learn a real solution. You don’t have heart failure, you’re not alone, and you don’t need to hydrate.

The real reason your hands are swelling

The reason your fingers are swelling is multifaceted but actually pretty simple. Before I explain I just want to clarify again that you’re fine, it happens to everyone and it’s totally normal and reversible.

The vasculature in your body is just a giant network of leaky plumbing. Imagine your body being a greenhouse with a sprinkler hose with hundreds of little holes running through it. The water that didn’t leave the hose is simply looped back around, much like your veins bring blood back to your heart. That hose brings essential fluid to the plants in that garden. Your vasculature in your arm is very similar to that garden hose. It runs down your arm, releases water into that tissue, and the excess water drains back to be recycled. When you step on that garden hose, aka put backpack straps on your upper arms, it increases pressure and increases the rate of that fluid shooting out of the uncountable tiny holes in the hose.

This is one cause of the swelling. Another cause is that the backpack straps essentially dam up the return flow like putting a wall in the trough. Now imagine there’s a drainage trough alongside the garden which returns the excess water from the soil to a pool where it can be recycled back into the hose to continue watering the plants. That is comparable to something in your body called the lymphatic system, which, much like a drainage trough, is a series of ducts which drain extra water in that extravascular space and recycles it back to your heart. By clamping down on those lymphatic ducts with backpack straps, it dams the trough, preventing fluid from draining from that extravascular space.

There’s another thing at play though. And if you’ve ever hiked with trekking poles while still wearing a hand swelling inducing backpack, you may be able to reason through that there has to be something else going on by the fact that trekking poles totally fix the problem. When we hike with trekking poles, even if we have the heaviest of backpack straps constricting our upper arms and shoulders, we don’t experience the swelling really at all. So it can’t just be the backpack straps causing it, especially since some people have this issue without wearing a backpack at all.

Something interesting about the cardiovascular system is that the blood pumping through our arteries, the big pulsating vessels we feel when we check our pulse, are almost entirely pumped by the heart. The heart contracts, much like squeezing a balloon full of water, and blood comes out of the hole. However, when the blood is returning back to the heart to be cycled again the blood is to a significant degree pumped because of contracting muscles in our limbs. They have one way valves in them so when we contract a muscle that is wrapped around a vein, it pumps the blood forward. And when that contraction ceases, the blood is unable to flow backwards. That repetitive contraction of our legs and arms pushes the blood forward, back to our heart. The reason we don’t experience edema in our legs on long hikes isn’t simply because of no backpack straps compressing the vasculature, but mostly because of our constantly contracting and relaxing leg muscles. When we use trekking poles, we continually contract the muscles in our arms and push that blood back toward the heart, preventing pooling by overcoming those barriers created by the backpack straps.

Additionally the trekking poles also likely benefit the swelling by shifting our shoulders frequently, releasing the pressure of the backpack straps on the upper arms, even if just for a second at a time. There could be an electrolyte component to it, but I find it exceedingly unlikely that this is a primary cause because the swelling would be consistent throughout the body, including the face, and I’ve only ever experienced and heard of people having swelling in their arms. Additionally, it takes a tremendous blow to knock the body’s electrolyte balance off. The body is very good at maintaining electrolytes in the blood in a very narrow range of values and the hyponatremia it would take to cause swelling would not only cause significant additional symptoms like nausea, vomiting, confusion, seizures, death, etc., but it’d also take a significant blow or underlying medical disorder to cause it.

Additionally, if dehydration were the issue, once again the swelling wouldn’t be isolated to the arms, and it’s also very uncommon for water to collect in the extravascular space when there is an overall deficit of water in the body. It can definitely happen but it’s rare and comparable to a dry paper towel sitting in a pool of water. The paper towel is going to soak up the water like our body is going to soak up that swelling.

Also, definitely not gravity as the primary culprit. If that were the case our legs which are much longer and have a much harder battle against gravity back to the heart so if gravity were the culprit our feet would be as thick as elephant stumps. And definitely not altitude: just go for a hike at sea level; it stills happens and there’s no reasonable mechanism. And just for completeness sake, it’s not temperature’s fault either. Once again, if that were the case, there’s no reasonable explanation for why it would be isolated to the hands and arms.

How to keep your hands from swelling

Now that I’ve explained the pathophysiology of hand swelling while hiking, I have a couple solutions. My first recommendation is using trekking poles, for so many reasons in addition to totally preventing the hand swelling. They help prevent injuries, make hiking easier, faster, and enable you to bounce down gnarly trails like a mountain goat. You’ll look dumb to everyone who has never used them but hey you already look dumb to everyone back at home relaxing on their sofas.

I highly recommend the Black Diamond Distance Z trekking poles.

If you absolutely refuse to use trekking poles or simply don’t hike often enough to drop the dough, I recommend you do some exercises while hiking. Take your hands and put your thumbs on your backpack straps and lift them off your shoulders. This will contract your muscles as well as relieve the pressure. It’ll also elevate your forearms to help promote some of that return flow. If you want to look extra special you could wave your hands in the air like you just don’t care, maybe show off your guns and flex a little for the single does prancing through the forest. If you want to look sooooper cool you could whip out the compression sleeves but I can’t imagine that helping much.

Or just get trekking poles and accept your fate that it’s impossible to look cool while hiking.

I am a long distance backpacker, triathlete, adventurer, climber, kayaker, and lowly medical student currently living in Norfolk, VA attending Eastern Virginia Medical School and getting out for adventures on weekends.

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8 thoughts on “Why your hands swell while hiking: the real reason”

I agree with you in the fact that the Lymphatic System is involved and edema is occurring when hands and fingers puff up. I also believe that the use of trekking poles helps as I’ve seen this anecdotally with my wife. Again, the lymph system is activated through the simple movement of the arms, thereby creating better circulation of the lymphatic system.

I’m not sure I buy into the backpack straps creating a tourniquet effect and contributing to the problem. My wife had problems many years ago just day hiking with no pack(sans poles) and used to regularly have swelling occur. (Again anecdotal) Do you have any research or studies that support the claim of backpacks contributing to the problem? If there is that much pressure occurring due to the backpack, and a waist belt is being utilized it seems to me the pack would not be fitted correctly.

I agree, hydration, electrolyte loss, etc is not contributing to the problem. It’s definitely seems to be a circulatory issue, likely confined to lymphatic circulation. If it was venous or arterial then you’d have temperature and color change in the extremities.

Thanks for your comment Matthew! I’ve never seen any research so it’s just a mechanism at best but it’s a realistic mechanism and the only reasonable one I’ve seen that’s been proposed. It’s definitely hard to globally diagnose likely hundreds of thousands if not millions of people with some sort of transient thoracic outlet syndrome but I figured it’s better than the garbage mechanisms I’d seen proposed online. I’m with you though that it can’t be isolated to simple compression of the backpack straps. I think it’s very likely largely due to lack of muscular contraction in addition to the compression or as an isolated mechanism itself. Once again, thanks for your feedback and I’m glad you liked the article!

I also suspect the centrifugal force of your swinging arms has something to do with it – all that force pushing the fluid outward, acting against the not-so-active lymphatic system in the arms. If you want to test the relative contribution of centrifugal force vs the other processes you mentioned, you could try hiking with your arms fixed at your sides, rather than swinging them 🙂

I am a long distance backpacker, triathlete, adventurer, climber, kayaker, and lowly medical student currently living in Norfolk, VA attending Eastern Virginia Medical School and writing about my adventures on my blog 'Because it's there' at www.graysoncobb.com

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